Gear pump

Abstract

The invention relates to a gear pump (1) for conveying a fluid, said gear pump comprising a rotatably mounted, external geared toothed wheel (3) and an internal geared annular gear (2) that are meshed in order to generate a conveying action, and are arranged together with an electrically commutable stator (7) in a housing (5). The stator (7) extends concentrically around the annular gear (2) and interacts with the annular gear to generate an electromotive force. The annular gear (2) has a closed, homogeneous cylindrical surface and a plain bearing (13) is provided on the stator (7).

Description

BACKGROUND OF THE INVENTION[0001]Rotary screw pumps comprise, amongst other things, internal gear pumps and annular gear pumps in which a driving gearwheel runs eccentrically in the internal tooth system of an annular gear. Internal gear pumps, which are particularly suitable for providing high pressures, are used to deliver fluids, for example to deliver fuel to an internal combustion engine.[0002]In the prior art, it is known to integrate internal gear pumps or annular gear pumps in an electronically commutated electric motor, with the rotor of the electric motor simultaneously being in the form of an annular gear of the internal gear pump or annular gear pump.[0003]DE 10 2006 007 554 A1 describes a delivery pump which is integrated in an electric motor. The delivery pump comprises a first gearwheel and a second gearwheel. A delivery space is formed between the two gearwheels. The second gearwheel is mounted at its centre on a mandrel. The first gearwheel is an external gearwheel ...

AI Technical Summary

Benefits of technology

[0008]The invention provides a gear pump for delivering a fluid, having a rotatably mounted externally toothed gearwheel and an internally toothed annular gear which engage in a meshing manner for the purpose of generating a delivery effect and which are arranged in a housing together with an electrically commutatable stator, with the stator extending around the annular gear in a concentric manner and interacting with the annular gear for the purpose of generating an electromotive force, and with the annular gear having a closed, homogeneous cylindrical surface and a sliding bearing being provided on the stator. A structurally simple and therefore cost-effective solution for mounting is provided by providing the sliding bearing directly on the stator.

[0012]The sliding bearing is preferably formed on the stator as a layer which is applied to a surface of the stator, this surface being opposite the annular gear, and therefore the sliding bearing is integrated in the stator. The stator, which can be a stator of a permanent-magnet motor or a reluctance motor, therefore advantageously acts on the inside diameter simultaneously as a radial bearing for the rotor which is designed as an annular gear or external annular gear of the internal gear pump or annular gear pump. The sliding bearing serves primarily as a wear-prevention layer between the stator and the rotor. In addition, the sliding bearing provides a centering function for the rotor and can reduce or prevent axial gap losses when provided with a corresponding design. This improves the efficiency of the electric motor.

[0014]According to a further preferred embodiment, the layer has a layer thickness which is less than or equal to 0.3 mm. Since a sliding bearing with a thin layer thickness is integrated in the stator, it is possible to ensure a correspondingly small air gap between the stator and the rotor, in particular when the motor is designed with a reluctance motor. Therefore, good efficiency of the electric motor can be presented.

[0016]Further preference is given to the layer being designed with a projection, and therefore the stator bearing against an inner wall of the housing with a prestress. In particular, the layer is designed such that the prestress has the effect of pressing the sliding bearing in the axial direction and correspondingly upward and against the inner wall when the cover is mounted. This does not create an air gap or creates a very small axial air gap, and accordingly only very minor gap losses occur.

Problems solved by technology

However, mounting of the annular gear, which has to adopt the drive torque of the electric motor, is problematical in configurations of this kind.

The solutions known in the prior art for mounting the annular gear in an internal gear pump or in an annular gear pump have a mechanically complicated design and are therefore structurally elaborate, complex and expensive in terms of production.

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